Unisolar Roofing [RE-wrenches]
Jeffrey Wolfe, Global Resources
global at sover.net
Wed Mar 14 21:01:11 PST 2001
Bill,
Thanks for the post. Eventually, we need a whole lot more data like this,
but this is the start, right? :)
Things like the manufacturer of the PV cells can make a difference in
annual output. But more so, things like PV technology and real weather have
a greater effect. (Single and poly crystal vs a-Si). So the annual numbers
will chage based on technology. Bigger change where the weather is less
uniform (like New England compared to AZ....)
I'm finding, (not yet really well supported, but coming up with the same
conclusion a couple ways) that on-grid batteryless, we're getting about
1000 kWh per kW installed. This si from some looking at the output of my
modules, some calcs based on combining all the efficiencies I READ for
equipment, and some on computer sims.
One factor that really differentiates single and poly crystal vs amorphous,
but is not well documented, is the "nominal" rating. The single and poly
crystals are "nominally" rated at a wattage higher than we'll ever see
(Solarex SX-120 rated at 120 watts, but really is btwn 110 and 120 Watts
due to wafer catagorizing, whereas the a-Si modules are typically rated at
there lowest performance point, with better summer performance.
So to compare apples to apples on price, space, etc., I'm about at the
point where I derate the crystal and polycrystal by about 10%, then
compare. ESPECIALLY on grid connect, where the majority of my kWh are
created in medium or hot weather (i.e. the sun is shining and the snow's
melted), and I can just about send the array south for the winter.
Jeff
Jeffery D. Wolfe, P.E.
Global Resource Options, LLP
A Woman-Owned Vermont Limited Liability Partnership
4 Kibling Hill Road
P.O. Box 51
Strafford, VT 05072
802/765-4632
802/765-9983 (Fax)
global at sover.net
http://www.globalresourceoptions.com
----------
From: Bill Brooks[SMTP:billbrooks7 at earthlink.net]
Reply To: RE-wrenches at topica.com
Sent: Wednesday, March 14, 2001 6:47 PM
To: RE-wrenches at topica.com
Subject: RE: Unisolar Roofing [RE-wrenches]
I realize that ASCII can be cruel, but hopefully you can read this. This is
top secret so make sure you spread it around ;-). This chart tells us the
impact of fixed orientation on annual energy production for a
grid-connected, net-metered PV system. Do not use this for off-grid since
we
cannot predict array utilization nearly as well. The interesting thing
about
this chart is that it clearly shows that annual energy producting is not
very sensitive to fairly wide variations in orientation (4:12 to 12:12, SE
to SW only has about 5% loss from ideal). Moral of the story is don't tilt
your modules on rooftop PV systems because it looks like hell, costs more
to
install, and often doesn't buy much as far as performance.
Roof pitch Flat 4:12 7:12 12:12 21:12 Vertical
South 0.89 0.97 1.00 0.97 0.89 0.58
SSE,SSW 0.89 0.97 0.99 0.96 0.88 0.59
SE, SW 0.89 0.95 0.96 0.93 0.85 0.60
ESE,WSW 0.89 0.92 0.91 0.87 0.79 0.57
E, W 0.89 0.88 0.84 0.78 0.70 0.52
Okay all you Wrenches out there, on the chart below are some real-life
numbers you should be using for grid-connect PV systems that are properly
oriented. This should generate some good controversy because nobody I know
states numbers this low. However, these are real-life conservative numbers.
A well installed system with minimal shading should be able to consistently
produce this much electricity or more in a year. If it doesn't, there is
something wrong with it (equipment or installation). The new California
Buydown guidelines require a meter come June 1, 2001, so sharpen your
pencil
because customers are now going to need energy estimates. This means you
need to do a detailed shading analysis with a Solar Pathfinder, use the
chart above to adjust for orientation, and multiply that number by your
location below and you're done! Piece of cake.
CITY kWh/kWstc
Arcata 1092
Shasta 1345
San Francisco 1379
Sacramento 1455
Fresno 1505
Santa Maria 1422
Barstow 1646
Los Angeles 1406
San Diego 1406
Anybody want to comment?
Bill.
> -----Original Message-----
> From: William Miller [mailto:wrmiller at slonet.org]
> Sent: Wednesday, March 14, 2001 2:13 PM
> To: RE-wrenches at topica.com
> Subject: RE: Unisolar Roofing [RE-wrenches]
>
>
> Bill:
>
> I am located in San Luis Obispo County. I have a client that
> installed his
> own ground mount array at 210 deg. true. I need to know in this type of
> situation, how much reduction in output will they have? I would like to
> own software that can determine this as it comes up frequently.
>
> William
>
>
>
> At 09:40 AM 3/14/01 -0800, you wrote:
> >Where are you located. I have a chart for the state of California. It
> >doesn't necessarily work in other locations. A similar chart was done
for
> >Colorado. It's just a series of PVFCHART simulations--works great.
> >
> >Bill.
> >
>
>
> __________________________________________________________________
> William Miller
> SLO Communications: Communications and Power Systems Consulting
> PO Box 50, Santa Margarita, CA 93453
> Voice :805-438-5600 Fax: 805-438-4607 VMail: 805-546-4875
> email: wrmiller at slonet.org
> License No. C-10-773985
> _____________________________________________________________
> Compatibility:
> Word processor: WP7
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> CAD: Microstation 95, DXF, Visio 4.1T
> _____________________________________________________________
> "I stand by all the misstatements that I've made." Dan Quayle
> __________________________________________________________________
>
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